Current transformers are inductive components that through their design with respect to imaging response and phase error enable precise acquisition of mains current in industrial meters as well as household meters. In combination with evaluation electronics they are now replacing the so-called Ferraris watt-meters (three-phase meters).
It is commonly known that such current transformers as well as other inductive components such as transformers for power supplies, chokes and repeaters can be produced on the basis of magnet cores affixed or molded in plastic housings. Here a magnet core provided with one winding or several windings is inserted in a thermoplastic housing and immersed in a molding resin generally consisting of polyurethane or epoxy resin. This causes numerous problems as regards outlets for the connecting cables from the windings. Providing outlets for the connecting cables through the molded surface demands precise positioning of the cable during the molding process. This generally requires the use of so-called molding pallets with cable fixtures. The use of such molding pallets is very costly.
A further possibility is to fasten the cable in a double groove on the upper edge of the housing. This, however, frequently leads to a discharge of molding resin as a consequence of capillary attraction through the groove.
A cable guide through a hole drilled in the wall of the housing requires additional sealing and hence additional cost which is economically disadvantageous.